Full Body Harness Research Articles

Safety Performance of the Full Harness in Various Falling Postures of Wearer

Fundamental safety measure for falling is to prepare flat and effective wide workplace with guardrails. However, their countermeasures may be difficult to apply for short-duration works and disaster relief works. In such cases, the fall arrest system has been applied to the height workplaces. This study focuses on fundamental characteristics of full body harness in various postures of wearer during falling. Three kinds of situation, such as (1) leg first fall, (2) head first fall, and (3) stop falling when the wearer body in parallel to the ground, were considered to recognize the performance. Experiments were carried out using 735N of human dummy, called HybridIII pedestrian 50%tile model in the automobile industry. The shock-absorber of the Lanyards used in this study were designed about 4kN. Impact force acting on hook, head accelerations, and a chest displacement were measured during falling. From the results, not only the vertical acceleration of the human dummy but also horizontal were measured. Due to the horizontal acceleration, a huge bending moment acting on the dummy's neck observed in several situations. It indicates that the wearer may have risks of whiplash or more serious injuries such as dislocation of cervical vertebrae or spinal injuries. Chest deformations measured in this study were not also small for aged workers. It indicates that there are some risks of rid fractures or related chest injuries. The back of the head crashed aggressively to the D-ring of the full harness when the dummy rebounded due to stop falling by lanyard. Therefore, special helmet to resist the impact force due to D-ring, and the design force of shock-absorber should be reconsidered.

Impact of Harness Fit on Suspension Tolerance

This study investigated the effect of body size and shape and harness fit on suspension tolerance time. Fall victims may develop suspension trauma, a potentially fatal reduction of return blood flow from legs to the heart and brain, after a successfully arrested fall if they are not rescued quickly or the harness does not fit them well. For this study, 20 men and 17 women with construction experience were suspended from the dorsal D-ring of a full-body fall-arrest harness. Their suspension tolerance time, physical characteristics, and harness fit levels were assessed. Body characteristics (i.e., weight, stature, upper- and lower-torso depths) were associated with decreased suspension tolerance time (r = -.36 - -.45, p < or = .03). In addition, harness fit affected suspension tolerance time; workers with a torso angle of suspension greater than 35 degrees, a thigh strap angle greater than 50 degrees, or a poorly fitting harness size had shorter suspension tolerance time (mean differences = 14, 11, and 9.8 min, respectively, p < or = .05). Body size and harness fit were predictors of suspension tolerance time. Selecting well-fit harnesses and establishing a 9-min rescue plan are suggested to ensure that no more than 5% of workers would experience suspension trauma. The study provides a basis for harness designers, standards writers, and manufacturers to improve harness configurations and testing requirements for better worker protection against suspension trauma.

Relationship Between Obesity and Falls by Middle-Aged and Older Women

Rosenblatt NJ, Grabiner MD. Relationship between obesity and falls by middle-aged and older women.It has been suggested that obesity increases fall risk, based on diminished static balance and increased fall-related injury risk. However, these findings only indirectly relate obesity and falls. The purpose of this study was to use existing data to directly explore the relationship between obesity and falls by community-dwelling women aged 55 years and older. Eighty-six subjects (42 obese) reported falls occurring during the previous year (retrospective falls), and over the following year responded to biweekly communications inquiring whether they fell or stumbled (prospective falls/stumbles). Because trips represent the largest fall cause by community-dwelling adults, we also analyzed outcomes and recovery strategies of 25 women (13 obese) after laboratory-induced trips. Obese and healthy weight women retrospectively reported similar fall rates (40.9% vs 40.5%; P=.97). Similar percentages of healthy weight and obese women prospectively fell (64.7% vs 64.3%; P=.98) and stumbled (38.9% vs 14.3%; P=.24). After laboratory-induced trips, 46.2% of obese verse 25.0% of healthy weight women fell (P=.44). Unlike healthy weight fallers, most obese fallers failed to initiate or complete the recovery step before full-body harness support. Obesity does not appear to increase overall fall risk; although, fall rates after laboratory-induced trips were notably higher, potentially due to altered recovery responses. An incomplete recovery step could increase impact force with the ground, predisposing obese individuals to injury. The fact that there is concurrence between 4 independent outcomes strengthens the findings, suggesting that further, large-scale studies are warranted to inform future clinical practice regarding fall-risk assessment for obese older adults.

Effects of Different Elastic Cord Assistance Levels on Vertical Jump

Tran, TT, Brown, LE, Coburn, JW, Lynn, SK, Dabbs, NC, Schick, MK, Schick, EE, Khamoui, AV, Uribe, BP, and Noffal, GJ. Effects of different elastic cord assistance levels on vertical jump. J Strength Cond Res 25(12): 3472-3478, 2011-Currently, little research has been conducted using body weight reduction (BWR) as a means to enhance vertical jump. The purpose of this study was to determine the effects of different elastic cord assistance levels on vertical jump height (JH), takeoff velocity (TOV), relative ground reaction force (rGRF), relative impact force (RIF), and descent velocity (DV). Thirty recreationally trained college men and women (M = 15, W = 15) completed 3 testing sessions consisting of 5 conditions: 0, 10, 20, 30, and 40% BWR. In all BWR conditions, the subjects wore a full body harness while being attached to 2 elastic cords suspended from the ceiling and a linear velocity transducer. They then performed 3 maximal countermovement jumps with arm swing on a force plate. The results indicated no interaction of condition by sex for any variable; however, there was a significant (p < 0.05) main effect for condition for each variable. The JH significantly increased across all conditions (0%: 43.73 ± 1.62 cm, 40%: 64.77 ± 2.36 cm). The TOV at 30% (2.73 ± 0.34 m·s) was significantly greater than that at 0% (2.59 ± 0.39 m·s) and 10% (2.63 ± 0.34 m·s), whereas that at 40% (2.79 ± 0.43 m·s) was significantly greater than that at >0, 10, and 20%. The rGRF at 30% (18.62 ± 4.35 N·kg) was significantly greater than that at >0, 10, and 20%, whereas that at 40% (21.38 ± 5.21 N·kg) was significantly greater than in all conditions. The RIF at 20, 30, and 40% (40%: 61.60 ± 18.53 N·kg) was significantly greater than that at 0% (44.46 ± 9.12 N·kg). The DV at 20% (2.61 ± 0.31 m·s) was significantly greater than at 10%, whereas those at 30 and 40% (2.8 ± 0.41 m·s) were significantly greater than at 0, 10, and 20%. These results demonstrate that using different elastic cord levels to reduce body weight appears effective for increasing ascent and descent force and velocity variables. Future research should investigate greater BWR% and chronic training.

Effect Of Elastic Assistance Vs. Bodyweight Training On Vertical Jump

Athletes who depend on vertical jump performance may benefit from integrating a training program that includes elastic assistance. Recent research has shown that training with low level elastic assistance may increase vertical jump height in comparison to training at body weight. PURPOSE: To determine the effects of 30% elastic assistance versus body weight training on vertical jump. METHODS: Sixteen recreationally trained male subjects (age 21.93 ± 2.04 yrs, height 173.64 ± 5.36 cm, mass 73.44 ± 3.90 kg) were divided into three groups: control (C), body weight (BW), or 30% body weight reduction (BWR). Training consisted of jumping 2 days a week for 6 weeks. In the BWR condition, subjects wore a full body harness that was attached to four elastic cords suspended from the ceiling as they completed maximal countermovement jumps with arm swing. Each group completed pre and post-tests of three maximal countermovement jumps in both conditions, (BW and BWR). All jumps were performed on a force plate. The training program progressively increased volume over the first five weeks, and then tapered on the 6th week. Maximum values for vertical jump height and relative ground reaction force (rGRF) were analyzed for each condition and time. RESULTS: Vertical jump collapsed across group demonstrated a significant (P<0.05) increase across time, (pre: 66.70 ± 2.20 cm, post: 69.54 ± 2.41 cm) and was significantly greater for BWR (75.92 ± 2.39 cm) than BW (59.76 ± 2.00 cm). For rGRF, there was a main effect for time and condition across group. The control group showed no significant (P>0.05) difference over time. The BW group significantly (P<0.05) increased over time, (pre: 16.65 ± 1.42 N/kg, post: 18.48 ± 1.27 N/kg) and it was significantly (P<0.05) greater with assistance, (BWR: 20.24 ± 1.96 N/kg, BW: 14.73 ±.82 N/kg). The BWR group significantly (P<0.05) increased over time, (pre: 18.25 ± 1.53 N/kg, post: 22.60 ± 2.41 N/kg) and it was significantly (P<0.05) greater with assistance, (BWR: 25.09 ± 2.1 N/kg, BW: 15.94 ± 1.3 N/kg). CONCLUSION: The greatest increases in rGRF were from the BWR group (∼24%) compared to the BW group (∼11%). Therefore, athletes who are dependent on the vertical jump for their specific sport should incorporate jumping with elastic assistance in their training program.

Effect of Different Levels of Assisted Jumping on Countermovement Unloading Force and Velocity

PURPOSE: The purpose of this study was to investigate the effect of elastic band assistance on VJ CM unloading force and velocity. METHODS: Thirty recreationally trained college men and women (M=15, W=15) completed three VJ testing sessions consisting of five conditions: 0%, 10%, 20%, 30%, and 40% body weight reduction (BWR). In all BWR conditions, subjects wore a full body harness while attached to two elastic cords suspended from the ceiling and performed three maximal VJ's with CM and arm swing on a force plate. In addition, a linear velocity transducer was attached to the subject's hip to determine the velocity-time curve. Percent unloading from body weight to minimal CM force and maximal CM velocity at each condition were recorded for analysis. RESULTS: Results indicated there were no sex by condition interactions (p>.05), but there were significant (p<.05) main effects for condition for both force and velocity. Countermovement unloading percentages were not different between 0% (64.62+22.51%) and 10% (70.75+14.41%), or between 20% (77.05+15.71%) and 30% (81.08+15.48%), or between 30% and 40% (83.88+13.79) BWR. Both 30% and 40% were greater than 10% and 0%, but only 40% was greater than 20%. CM velocities under all elastic conditions were significantly faster than 0% (0%=.99+.25 m/s, 10%=1.19+.26 m/s, 20%=1.24+.30 m/s, 30%=1.29+.26 m/s, 40%=1.23+.17 m/s). Only 30% was significantly faster than 10%. CONCLUSIONS: These data suggest that assisted jumping alters countermovement mechanics. Therefore, future research should investigate the chronic effects of assisted jumping on normal bodyweight VJ performance.

Effects of Assisted Jumping on Relative Impact Force and Descent Velocity

Unassisted increased jump height subsequently increases descending velocity resulting in increased impact forces. Increased impact forces produce greater eccentric forces, which may lead to greater muscular adaptations. This is less well understood during an assisted jump. PURPOSE: The purpose of this study was to investigate the effects of different assisted jumping conditions on relative impact forces (RIF) and descent velocity (DV). METHODS: Thirty recreationally trained subjects (male = 15, female = 15) completed three testing sessions consisting of five experimental conditions: body weight reduction (BWR) of 0%, 10%, 20%, 30%, or 40%. In all conditions, subjects wore a full body harness while attached to two elastic cords, suspended and bolted to the ceiling. Subjects performed three maximal countermovement jumps with arm swing on a force plate with a velocity transducer for each condition. Maximum jump height (JH) values using a vertec for each condition were used for analyses. RESULTS: JH significantly (p < 0.05) increased across conditions (0% = 35.14 ± 9.02 cm, 40% = 79.44 ± 14.12 cm). Additionally, DV at 30% and 40% were significantly greater than 0%, 10%, and 20%, however, no differences were found between 30% and 40% (0% = 2.57 ± 0.30 m/s, 40% = 2.78 ± 0.35 m/s). Lastly, RIF was significantly greater across conditions from 10–30% (0% = 44.46 ± 9.12 N/kg, 30% = 57.66 ± 19.16 N/kg) when compared to 0%. Conclusion: Increased DV coupled with decreased body weight greater than 30% results in increased relative eccentric forces. Practical Applications: Assisted jumping at BWR ≥ 30% may augment eccentric forces and enhance muscular adaptations.

The Effect of the Use of Full Body Harnesses on Their Protective Properties

A full body harness is a component of personal systems protecting against falls from a height. To ensure users’ safety, the harness must retain its protective properties during its whole service period. All the elements of a harness (webbings, threads, metal buckles, etc.) are exposed to destructive factors. Harnesses stored and used for a few years were tested. The paper discusses the most frequent types of damage and their effect on the essential resistance parameters. The effect of atmospheric conditions, sunlight, mechanical damage and dust on the parameters of webbings was tested. Conclusions on the main causes of the loss of the protective properties of harnesses are drawn; periodic checks of the physical conditions and guidelines for estimating acceptable service time are recommended.

Suspension Tolerance in a Full-Body Safety Harness, and a Prototype Harness Accessory

Workers wearing full-body safety harnesses are at risk for suspension trauma if they are not rescued in 5 to 30 min after a successfully arrested fall. Suspension trauma, which may be fatal, occurs when a person's legs are immobile in a vertical posture, leading to the pooling of blood in the legs, pelvis, and abdomen, and the reduction of return blood flow to the heart and brain. To measure suspension tolerance time, 22 men and 18 women with construction experience were suspended from the chest D-ring (CHEST) and back D-ring (BACK) of full-body, fall-arrest harnesses. Fifteen men and 13 women from the original group of subjects were then suspended using a newly developed National Institute for Occupational Safety and Health harness accessory (ACCESS), which supports the upper legs. Midthigh circumference changes were 1.4 and 1.9 cm, changes in minute ventilation were 1.2 and 1.5 L/min, changes in heart rate (HR) were 15.1 and 21.6 bpm, and changes in mean arterial pressure were 5.1 and −2.6 mmHg (p ≤ 0.05) for all subjects during CHEST and BACK, respectively. Kaplan-Meier median suspension time for all subjects for the CHEST condition was 29 min (range 4–60 min) and 31 min (range 5–56 min) for the BACK condition. The 95th percentile for suspension time was 7 min for CHEST and 11 min for BACK. Cox regression revealed that body weight had a statistically significant effect on the time until experiencing a medical end point (p ≤ 0.05) during the BACK condition. Mean (± SD) suspension time was 58 ± 6 min (range 39–60 min) for all subjects for the ACCESS condition. There were no terminations due to medical symptoms during the ACCESS suspension, changes in physiological variables were small, and 85% of ACCESS subjects completed 60-min suspensions. These data provide information on motionless suspension tolerance time to standards-setting organizations and demonstrate the potential of a prototype harness accessory to delay or prevent suspension trauma.

The Influence of Anchor Devices on the Performance of Retractable Type Fall Arresters Protecting Against Falls From a Height

Retractable type fall arresters are part of the equipment used for protecting people against falls from a height. They are an intermediate part between full body harness worn by a man and the structural anchor at the worksite. The most important task of retractable type fall arresters is to arrest people’s falls and to reduce their harmful consequences. Information received from users as well as laboratories testing protective equipment indicates that the performance of such equipment is incorrect under specific conditions. The paper is concerned with an analysis of the conditions in which retractable type fall arresters demonstrate intermittent performance and with an explanation of that phenomenon. The results of tests investigating anchor devices and the performance of retractable type fall arresters are presented. External and internal factors contributing to intermittent performance have been determined and guidelines for safer use of these devices have been developed.